Sulfonate lubricating grease



Patented July 31, 1951 2562314 u SULFONATELUBRICATING GREASE nosemaryonailoa, Elizabeth, N. J., assigner to Standard Oil'Develo poration of Delaware pment Company, a cor- ,"ApliieauonMarch 5, 1949, serial No. '193.21

The present invention relates to lubricatingA grease compositions, and particularly to lubricat-I ing greases prepared from lubricating oils which are thickened with materials other than the con-v ventional soaps. applicable to new types of `.lubricating greases which contain a mixture or a complex of oil soluu ble and oil insoluble materials, such as oil soluble sulfonates and oil insoluble salts of low molecular Weight as the thickening agent.

Recently, several suggestions have been made that the soap content of normal lubricatingV -greases may be largely or entirely replaced by a mixture or a complex of an oil soluble petroleum sulfonate ,with an oil insoluble, or relatively in- `soluble salt of low molecular Weight acid. A

grease consisting of lubricating oil thickened to grease consistency with a Vmixture of oil soluble metal sulfonate and an alkali or alkaline. earth metal acetate may be considered' as .an example. 20

Salts of other low molecular Weight acids, organic and inorganic, have been-suggested for this purpose- .u

Greases of the type referred to above comprise a suitable lubricating oil, preferably mineral base lubricating oil, which may be thickened to grease consistency With about 5 to 20 by weight, based upon the total composition, of an oil 'soluble metal sulfonate combined with 0.5 vto 'about l5 or 16% by Weight of oil insoluble metal salt. The oil soluble metal sulfonate may' beprepared in a conventional Way from a sulfonio acid having a molecular Weight somewhatabove 400LYfor-example 450 or 475. Such sulfonic acids are Vcoml" monly obtained by treating mineral oils of Is'uitable grade with concentrated'or fumng sulfuric acid. The salts are obtained byneutralizingiwith metal oxide, hydroxide or carbonate.

The sulfonates of alkaline earth metals aref.`

preferred, especially strontium or calcium sul* 40,

fonates, but the alkali metal sulfonates, especially sodium sulfonate, may be used for some purposes. The oil insoluble metal salt which Yis mixed or complexed with the oil soluble sulionate is'v" preferably an alkaline earth metal salt of a low molecular Weight fatty acid. Calcium acetate is a preferred material, but the corresponding salts of other loW molecular Weight acids, for example,

the propionate, formate, butyrate, lactate, cai-v bonate, nitrate, chloride, the sulfonates of low molecular Weight such as those of methane or ethane sulfonic acids, etc., may be used.; `In lieu of the calcium salt, like Salts of the other lalkaline earth metals or of the alkali metals maybe' used. Mixtures of these salts can of course ybe employed ifrdesired. In greases of this type, the inorganic salt attracts thev oil soluble rsulfonate particles toV form micelles, which on a very lmi-r nute scale, may be compared to tangles orbrush=A-x 15 Claims. (Cl. 252-333) The invention is particularly 5 30V'abietic'acid. Tall'oilesters, oleate esters,

. 2 i heaps" which set up a solid structure, holding the oil in the colloid. This protective colloid is beneficial in increasing the droppin-g point of the grease, bit when highV concentrations are employed the grease is non-homogeneous. Such greases are grainy and are not satisfactory. The particles or granules in such a grease can be felt with the fingers and seen with the unaided eye. They prevent the grease from lubricating properly. They cannot be removed by filtration.

The essence of the present invention is the: addition to greasesof this general type of a modier which prevents the formation of granular particles. The incorporation of the modifier,y according to this invention,l produces a grease which islhomogeneous without being excessively soft in structure, and which` retains the excellent properties such as high dropping point, resistance to bleeding, etc., of the unmodied grease.

Inl the preferred embodiment, the modiiier is .a substantially 4,fully es teri'fied, @aliphatic polygroups, the Cie to C20 acids being especially preferred. The trioleate ester of sorbitan is Avery good for this purpose. Analogous 5cheaper hiaterials such as the tall oilA ester ofethylene glycol or propylene glycol mayjbev used, commercial ltall oil being largely a `mixture of oleic acid and and thev analogousfstearates, palmitates, hydroxystearates, -ricinoleates', and the like, may be formed from' sorbitol, sorbitan, mannitol, `dulcitan,l pentaerythritol, diphentaerythritol, lglycerine, polyglycols, vpolyalkylene glycols, p olyoxyalkyleneglycols, and thev like, with satisfactory results.v I\l`atu`rall fats, lbeing mixed esters of glycerol`,are also "suitable materials.' Ordinary esters such as hydrogenatedf'ats of natural cc# furrence, e. g. hydrogehated'ltalliv may be used.

Ilfhev use of partial esters, such 'as' `-pentaeryth1jitol monooleateor srbitanrnonoolleate' is possible When soft greases are desired', but'vvhen vgreas'es of firm structure are desired the completely esteru ied polyh'ydroxy. alcohol preferred. s n.,

`A characteristic of these modifying materials is that when reacted with calcium acetate in the absence of sulfonate they form products varying from viscous liquids to mushy semi-solids, but in allA cases the products are. homogeneous. `This compatibility with calcium acetate isapparently essential. Materials which.. areV vunsatisfactory for the purposes ofthe invention are usuallynot compatible with calcium acetate, for example'in hydroxy esters which precipitate a white insolu-` ble complex and the low molecular weight esters which precipitate a granulated solid on being mixedwith"'calcium acetate.

gen pressure drop) The preferred grease, for purposes of the present invention, comprises about 65 to 94% by weight of oil of lubricating grade, thickened with 5 to 20% of oilA soluble metal sulfonatesv derived from the petroleum sulfonates of molecular Weight above about 400. These sulfonates are combined with 0.5 to of a suitable low molecular weight salt, especially the calcium salt of C1 to C4. aliphatic acids. This base grease material has combined with it from 0.5 to 5%, preferably from 1 to 3%, of the modi'er. It is essential that the modifier be incorporated with the sulfonate prior to the addition of the calcium acetate or other oil-insoluble salt, since the addi- As indicated above, it has been found in this connection that wholly esteried polyhydric compounds are the most desirable. Hydrogenated tallow may be used and others of the most common fats and hydrogenated fats of natural origin are quite satisfactory. Partially esterified polyhydric compounds also exert a modifying action, (Examples V and VI), but they result in a grease Which is much softer and not noticeably easier to handle. The following data will illustrate this point. The grease in each case was prepared as described above in Example I, except that the modifier was varied. 2% by weight of modifier was used in each case.

TABLE II Elect of modifier on strontium sulfonate-calcium acetate grease ase o a ion ter Ex Ester Type Filtering l0 Passes Microworker 1....- Sorbitan Trioleate Crzlipltlly Estericd Polyhydric Good 271 co o II.. Polyoxyethylene Stearate Fair 277 III. Ethyleneglycol Tall Oil Ester Good 254 IV-.. Hydrogenated Tallow do .do... 276 V Sorbitan Monooleate Partially Esteriied Polyhydric A1 hol. .do 291 VI... Ethyleneglycol Monooleate do F 315 VII-- Isopropyl Oleate Esteried Monohydric Alcohol Very Poor.. 200

tion of the .modier to an already formed sulfonate acetate complex is not effective.

The invention will be more fully understood by reference to the following examples:

EXAMPLE I A grease prepared from 10% strontium petroleum sulfonate based on sulfonic acids of 450 molecular weight, 10% calcium acetate, and 2% sorbitan trioleate +0.5% phenyl alpha naphthylamine dispersed in mineral base oil of 55 S. U. S. viscosity at 210 F. appears superior to a conventional soda-lime anti-friction bearing grease, showing higher dropping point (500 F.+vs 350 FJ, superior performance in the BEC bearing test at 200 F. (20% vs. 73% loss), superior wheel bearing test performance, and better oxidation stability (246 hours vs. 126 hours to 5 p. s. i. oxy- 'I'he apparent viscosity of the grease also is within the range generally associated with soap thickened greases as shown in attached Figure 1. By contrast, a mixture of l' 10% strontium sulfonate and 10% calcium acetate in the same mineral oil Without the sorbitan trioleate was excessively hard and could not be filtered to a grease-like material.

The following table shows a comparison of the above grease with a conventonalhigh grade ball bearing lubricant of substantially the same overall salt (soap) content.

TABLE I Comparison with conventional bearing greases Conventional Soda Lime Example I Ball Bearing Lubricant As will be obvious to those skilled in the art, various additives which are conventional in greases may be used. Materials such as antioxidants, rust inhibitors, corrosion inhibitors,` extreme pressure agents, oiliness additives,.and the like, may be incorporated. The type of lubricating oil may be varied widely, e. g., mineral base oil of 50 to 1000 or more S. U. S. viscosity at F., or certain of the synthetic oils such as the esters of dibasic acids may be used alone or in combination with mineral oils. Conventional soap-type thickeners may be combined with the sulfonate-salt type thickeners, if desired, for example, by the incorporation of a limited amount of the soap-type thickener during grease manufacture, or by mechanical mixture of performed soap thickened grease with the sulfonate-type grease.

In the appended claims, mineral base oil refers to oils which are essentially or predominantly of petroleum derivation, but may also include significant amounts of conventional synthetics, thickeners, and the like, as will be obvious to those skilled in the art.

What is claimed is:

1. A lubricating grease composition consisting essentially of a lubricating oil thickened to a grease consistency with a complex combined thickener of 5 to 20% by weight, based on the total composition, of oil soluble metal sulfonate derived from relatively high molecular weight petroleum sulfonic acids combined with 0.5 to 15% by weight of an oil insoluble metal salt of relatively low molecular weight acid, and a structure modifier comprising 0.1 to 5% of an ester of polyhydric alcohol and organic acid of 12 to 24 carbon atoms.

2. Composition of claim l wherein said structure modifier is a C12 to C2i fatty acid substantially complete ester of an aliphatic polyhydric alcohol.

3. Composition of claim 1 wherein said structure modifier is a substantially complete C12 to C24 fatty acid ester of an aliphatic polyhydric ,alcohol of .2 to 6 hydroxyl groups.

4. Composition of claim 1 wherein said structure modified is a substantially complete Cia fatty acid ester of an aliphatic polyhydric alcohol.

5. Composition of claim 1 wherein said structure modifier is a substantially complete Cia ester of sorbitan.

6. Composition of claim 1 wherein said structure modifier is hydrogenated tallow.

7. Composition as structure modier is polyoxyethylene stearate.

8. Composition of claim 1 in which said structure modier is a substantially complete ester of a partially dehydrated hexahydric alcohol.

9. A lubricating grease composition consisting essentially of 65 to 94% by weight of mineral base lubricating oil, 5 to 20% based on the total composition of oil a complex combined thickener comprising soluble metal sulfonate derived from petroleum base sulfonic acids of` at least 400 molecular weight. 0.5 to 15% of alkaline earth metal salt of C1 to C4 fatty acid. and 0.1 to 5% of a substantially fully esteried C12 to C24. fatty acid ester of a partially dehydrated polyjhydric alcohol.

10. Composition as in claim 9 wherein said ester is a C16 to Czotri-ester of sorbitan.

11. Composition as in claim 9 wherein said ester is sorbitan esteriiled with at least two oleate groups. g l

12. Composition `as in claim 9 wherein said ester is sorbitan trioleate.

13. Composition as in claim 9 wherein said ester is ethylene glycol tall oil ester.

14. A lubricating grease composition consisting essentially of lubricating oil, thickened to a in claim 1 in which said lili grease consistency with a complex thlckener comprising a mixture of oil soluble strontium petroleum sulfonate and calcium acetate, and from 0.1 to 5% by weight. based on the total composition, of a substantially fully esteried Cie to Cza fatty acid ester of an aliphatic polyhydric alcohol which has 2 to 6 carbon atoms.

15. A method for preparing a lubricating grease which comprises blending about 65-94% by weight based on the total composition of a mineral base lubricating o, 5 to 20% of an oil soluble metal sulfonate derived from petroleum base sulfonic acids and 0.1 to 5% of an ester of polyhydric alcohol and organic acid of 12 to 24 carbon atoms, forming a homogeneous mixture of the aforesaid ingredients, and thereafter incorporating 0.5 to 15% by weight of an oil insoluble metal salt of a relatively low molecular weight acid to form with said sulfonate a complex thickener.

ROSEMARY OHALLORAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH A COMPLEX COMBINED THICKENER OF 5 TO 20% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF OIL SOLUBL EMETAL SULFONATE DERIVED FROM RELATIVELY HIGH MOLEUCLAR WEIGHT PETROLEUM SULFONIC ACIDS COMBINED WITH 0.5 TO 15% BY WEIGHT OF AN OIL INSOLUBLE METAL SALT OF RELATIVELY LOW MOLECULAR WEIGHT ACID, AND A STRUCTURE MODIFIER COMPRISING 0.1 TO 5% OF AN ESTER OF POLYHYDRIC ALCOHOL AND ORGANIC ACID OF 12 TO 24 CARBON ATOMS. 